Lens



L. W. BUGBEE.

LENS.

APPLICATION FILED DEC. 13. 1916.

Patented July 20, 1920.

L v x fz 1) H616]? ll Q? BY J ATTOR/VEKS UNETED STATES PATENT OFFICE.

LUCIAN W. BUG-BEE, 0F SOUTHBRIDG-E, MASSACHUSETTS, ASSIGNOR TO AMERICAN OPTICAL COMPANY, OF 'SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARY ASSOCIA- rron or mnssncnusnrrs.

LENS.

Specification of Letters Patent. Patented July 20, 1920.

Application filed December 13, 1916. Serial No. 136,686.

To all whom it may concern:

Be it known that I, LporAN W. BUGBEE, a citizen of the United States, residing at Southbridge, in the county of Worcester and State of Massachusetts, have invented certain new and useful Improvements in Lenses,

of which the following is a specification.

My invention relates to improvements in lenses and has particular reference to an improved construction of lens formed in two or more parts.

One of the leading objects of my present invention is the provision of an improved construction of a two part lens in which the parts shall be separably united but shall be held in a very firm and secure manner, which will resist to a maximum accidental relative shifting or disarrangement of the parts.

A further object .of the present invention is the'provision of an improved construction of lens and of an improved cement or adhesive medium for uniting the parts of said lens, which will have sufficient strength to allow the parts to be ground if desired after cementing and will resist the tendency of the parts to shift during the grinding operation.

Another object of my invention is the provision of an improved securing medium for uniting the two parts of the lens, which shall have substantially thesame coefficient of expansion as the parts of the lens or substance to be united, and which shall have sufficient elasticity or expansion and contraction to automatically accommodateitself to the changing of the parts due to varying temperatures, and will prevent their cracking apart or becoming separated due to unequal expansion of the cement and united parts.

A further object of the invention is the provision of an improved transparent adhesive which will securely retain together glass'or other polished surfaces and prevent either direct separation or accidental relative lateral or sliding movement of the parts.

Other objects and advantages of my improved construction should be readily apparent by. reference to the following depended claims without departing from or exceeding the spirit of my invention. v

Flgure I represents a plan view of a lens embodying my improvement.

F'g. II represents a sectional view thereof.

Fig. III represents a sectional view of a different construction of lens.

In the drawings, the numeral 1 desi nates the larger or major portion of the lens blank and the numeral 2 the segment or reading portion. It is to beunderstood that this segment may be either secured to one face of the lens, as illustrated for example in Fig. II, or may be set into a countersink formed into the face of the lens, as indicated in Fig. III, my cement being applicable to either form or to any other form of lens or transparent members to be united, but being particularly desirable for use in connection with the form illustrated in Fig. III.

In the formation of bifocal lenses of various types a certain amount of difficulty has which will adhere to the polished surfaces of the lenses, which will in no wise cloud or impair the optical valueofithe surfaces, which will be substantially colorless, and which will have the same refractive index and coefficient of expansion as at least one of'the parts to be united so that there will be no optical defects introduced into the lens on account of the use of the cement, and so that the wafer will be satisfactorily retained under varying weather conditions or the like and will not become separated or fall off due to unequal expansion in the cement and wafer under rapid temperature changes, such as coming in from out doors into a warm room, or vice versa.

It has also been found desirable in some instances in the past in the construction of bifocals or other lens constructions, to unite two lenses with either polished or unpolished surfaces together and to subsequently subject the parts to a grinding action, which grinding action will generate both heat and lateral friction tending to cause the parts to slide one over the other.

Particularly speaking, therefore, my present invention particularly relates to the provision of an improved lens or the like which will overcome the objections hitherto present in connection with cemented or removably secured lens parts and which will securely will lock the parts against accidental relative lateral or sliding movement, but will permit of separation of the parts as desired.

For example, in the forms of my invention illustrated in both Figs. 11 and III, the major blank or portion 1 and the segment 2 are each ground and polished to necessary curvature and the face of the segment which'is to be disposed toward the main blank is ground to the same exact curve as the face ofthe blank which it 'is to engage so that the parts may satisfactorily fit one against the other.

To then unite the two polished surfaces I make useof my improved cement, adhesive or connecting medium, which medium may becompounded for example, of a suitable gunnsuch as Canada balsam for example, which will be transparent when in a thin film'and will have substantially the coeflicient of expansion and the refractive index of one of the parts to beunited, said gum being charged to a suitable degree with finely powdered or comminuted glass or like transparent mineral matter, the cement being found to work to best advantage when charged as fully as possible with the inert or mineral matter.

In joining the surfaces I then suitably coat one or both surfaces with this cement, the several parts being in heated condition to render the cement soft or plastic, and press the two parts to be united firmly together to reduce the cement to the thinnest possible film therebetween and allow the same to harden or become set.

It will then be found thatthe balsam gum mixed with the particles of glass has substantially the same index of refraction as the parts .to be united. Thus the balsam will provide a thin colorless transparent film and at the same time will satisfactorily cling to the two polished surfaces to be joined, while the glass charged the-reintowill insure the parts being of the same coefficient of expansion and at the same time the sharp edges of the pulverized or powdered glass will have a tendency to bite into or frictionally engage the polished surfaces of the parts being united andwill resist relative sliding of the parts one over the other, counterbalancing the well known lubricating tendency of an ordinary adhesive.

I claim:

1. An ophthalmic lens, comprising a plurality of parts adapted to be joined one to the other, said parts having polished contacting surfaces, and an adhesive interposed between said parts and comprising a powdered transparent mineral matter and a gum which is transparent in a thin film.

2. An ophthalmic lens, comprising a plurality of separate parts, which parts are separably united by a transparent adhesive charged with comminuted particles having substantially the same composition as that of one of the parts to be united whereby the uniting film will have substantially the same coefiieient of expansion as said part.

3. A transparent cement, comprising an inert transparent powder having substan tially the coefficient of expansion and refractive index of the substance to which it is to be applied, and an adhesive body or binder of, a substance possessing substantially corresponding coefiicient of expansion and index of refraction, and which will be transparent in a thin film. I

4L. An ophthalmic lens comprising a major portion of one refractive index having a countersink formed therein and a segment of different index having one face formed curved to fit the countersink and a uniting medium interposed between said parts, said uniting medium including a transparent cementitious material and transparent comminuted glass particles combined therewith substantially as and for the purpose de- Y scribed.

v5. An ophthalmic lens comprising a major portion of one refractive index having a countersink formed therein and a segment of different refractive index having one face formed to fit the countersink, a uniting medium interposed between said parts, said uniting medium including a transparent cementitious material having substantially the same index of refraction as the major portion, and having transparent glass particles of similar index-of refraction combined therewith, substantially as and for the purpose described.

In testimony whereof I affix my signature in the presence of two witnesses.

LUOIAN W. BUGBEE.

Witnesses:

H. la. PARSONS, EDITH M. HALVORSEN. 

